package com.github.kezhenxu94.playground.leetcode;

/**
 * 121. Best Time to Buy and Sell Stock
 * 
 * Say you have an array for which the ith element is the price of a given stock
 * on day i.
 * 
 * If you were only permitted to complete at most one transaction (ie, buy one
 * and sell one share of the stock), design an algorithm to find the maximum
 * profit.
 * 
 * Example 1:
 * 
 * Input: [7, 1, 5, 3, 6, 4] Output: 5
 * 
 * max. difference = 6-1 = 5 (not 7-1 = 6, as selling price needs to be larger
 * than buying price)
 * 
 * Example 2:
 * 
 * Input: [7, 6, 4, 3, 1] Output: 0
 * 
 * In this case, no transaction is done, i.e. max profit = 0.
 * 
 * @author ke.zhen.xu
 *
 */
public class Solution121BestTimeToBuyAndSellStock {

	/**
	 * Violent solution
	 * Time Limit Exceeded
	 * 
	 * TODO Optimize
	 * 
	 * @param prices
	 * @return
	 */
	public int maxProfit(int[] prices) {
		int maxProfit = 0;
		for (int i = prices.length - 1; i >= 0; i--) {
			int maxSell = prices[i];
			for (int j = i + 1; j < prices.length; j++) {
				if (prices[j] > maxSell) {
					maxSell = prices[j];
				}
			}
			if (maxProfit < maxSell - prices[i])
				maxProfit = maxSell - prices[i];
		}
		return maxProfit;
	}

}
